DOCSLIB.ORG

Structure Property Relations in Complex Copolymer Systems

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Structure Property Relations in Complex Copolymer Systems Structure Property Relations in Complex Copolymer Systems Dissertation zur Erlangung des Grades ‚Doktor der Naturwissenschaften’ am Fachbereich Chemie der Johannes Gutenberg-Universität in Mainz Ahmad Azhar Juhari Mainz, 2010 Datum der mündlichen Prüfung: 26. Juli 2010 Abstract A thorough investigation was made of the structure-property relation of well- defined statistical, gradient and block copolymers of various compositions. Among the copolymers studied were those which were synthesized using isobornyl acrylate (IBA) and n-butyl acrylate (nBA) monomer units. The copolymers exhibited several unique properties that make them suitable materials for a range of applications. The thermomechanical properties of these new materials were compared to acrylate homopolymers. By the proper choice of the IBA/nBA monomer ratio, it was possible to tune the glass transition temperature of the statistical P(IBA-co-nBA) copolymers. The measured Tg’s of the copolymers with different IBA/nBA monomer ratios followed a trend that fitted well with the Fox equation prediction. While statistical copolymers showed a single glass transition (Tg between -50 and 90 ºC depending on composition), DSC block copolymers showed two Tg’s and the gradient copolymer showed a single, but very broad, glass transition. PMBL-PBA-PMBL triblock copolymers of different composition ratios were also studied and revealed a microphase separated morphology of mostly cylindrical PMBL domains hexagonally arranged in the PBA matrix. DMA studies confirmed the phase separated morphology of the copolymers. Tensile studies showed the linear PMBL-PBA-PMBL triblock copolymers having a relatively low elongation at break that was increased by replacing the PMBL hard blocks with the less brittle random PMBL-r-PMMA blocks. The 10- and 20-arm PBA-PMBL copolymers which were studied revealed even more unique properties. SAXS results showed a mixture of cylindrical PMBL domains hexagonally arranged in the PBA matrix, as well as lamellar. Despite PMBL’s brittleness, the triblock and multi-arm PBA-PMBL copolymers could become suitable materials for high temperature applications due to PMBL’s high glass transition temperature and high thermal stability. The structure- property relation of multi-arm star PBA-PMMA block copolymers was also investigated. Small-angle X-ray scattering revealed a phase separated morphology 4 of cylindrical PMMA domains hexagonally arranged in the PBA matrix. DMA studies found that these materials possess typical elastomeric behavior in a broad range of service temperatures up to at least 250°C. The ultimate tensile strength and the elastic modulus of the 10- and 20-arm star PBA-PMMA block copolymers are significantly higher than those of their 3-arm or linear ABA type counterparts with similar composition, indicating a strong effect of the number of arms on the tensile properties. Siloxane-based copolymers were also studied and one of the main objectives here was to examine the possibility to synthesize trifluoropropyl- containing siloxane copolymers of gradient distribution of trifluoropropyl groups along the chain. DMA results of the PDMS-PMTFPS siloxane copolymers synthesized via simultaneous copolymerization showed that due to the large difference in reactivity rates of 2,4,6-tris(3,3,3-trifluoropropyl)-2,4,6- trimethylcyclotrisiloxane (F) and hexamethylcyclotrisiloxane (D), a copolymer of almost block structure containing only a narrow intermediate fragment with gradient distribution of the component units was obtained. A more dispersed distribution of the trifluoropropyl groups was obtained by the semi-batch copolymerization process, as the DMA results revealed more ‘‘pure gradient type’’ features for the siloxane copolymers which were synthesized by adding F at a controlled rate to the polymerization of the less reactive D. As with trifluoropropyl-containing siloxane copolymers, vinyl-containing polysiloxanes may be converted to a variety of useful polysiloxane materials by chemical modification. But much like the trifluoropropyl-containing siloxane copolymers, as a result of so much difference in the reactivities between the component units 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (V) and hexamethylcyclotrisiloxane (D), thermal and mechanical properties of the PDMS-PMVS copolymers obtained by simultaneous copolymerization was similar to those of block copolymers. Only the copolymers obtained by semi-batch method showed properties typical for gradient copolymers. 5 Table of Contents ABSTRACT .................................................................................................................................... 4 OVERVIEW.................................................................................................................................... 8 INTRODUCTION & MOTIVATION ........................................................................................ 10 1 METHODOLOGICAL SYSTEMS.................................................................................... 15 1.1 DYNAMIC MECHANICAL ANALYSIS ............................................................................... 15 1.1.1 Definitions................................................................................................................. 15 1.1.2 Oscillatory response of real systems......................................................................... 23 1.1.3 Mechanical models of linear viscoelasticity ............................................................. 27 1.1.4 Thermorheological simplicity and time-Temperature superposition........................ 32 1.1.5 Origin of the liquid-to-glass “transition”................................................................. 36 1.1.6 Proposed fit function for the master curve................................................................ 47 1.2 SMALL ANGLE X-RAY SCATTERING .............................................................................. 48 1.2.1 Bragg’s law............................................................................................................... 49 2 MATERIALS & THEIR CHARACTERIZATION ......................................................... 52 2.1 ACRYLATE-BASED LINEAR COPOLYMERS...................................................................... 52 2.2 ACRYLATE-BASED TRIBLOCK AND MULTI-ARM BLOCK COPOLYMERS.......................... 55 2.2.1 PMBL-PBA-PMBL triblock copolymers................................................................... 56 2.2.2 PBA-PMBL multi-arm block copolymers.................................................................. 57 2.2.3 PBA-PMMA multi-arm block copolymers ................................................................ 59 2.3 SILOXANE-BASED LINEAR GRADIENT COPOLYMERS ..................................................... 60 2.3.1 Fluorosiloxane-based copolymers ............................................................................ 60 2.3.2 Vinylsiloxane-based copolymers............................................................................... 62 2.4 MATERIAL CHARACTERIZATION .................................................................................... 63 2.4.1 Dynamic mechanical analyses (DMA)...................................................................... 63 2.4.2 Differential scanning calorimetry (DSC).................................................................. 65 2.4.3 Small-angle X-ray scattering (SAXS) analyses ......................................................... 65 2.4.4 Tensile tests............................................................................................................... 65 3 RESULTS & DISCUSSION................................................................................................ 66 3.1 COMPARING ACRYLATE-BASED COPOLYMERS TO HOMOPOLYMERS ............................. 66 3.1.1 Statistical P(IBA-co-nBA) copolymers...................................................................... 66 6 3.1.2 Statistical copolymers mimicking homopolymers. .................................................... 73 3.1.3 Gradient P(IBA-grad-nBA) and block PIBA-b-PnBA copolymers ........................... 76 3.2 ACRYLATE-BASED BLOCK COPOLYMERS AS THERMOPLASTIC ELASTOMERS ................ 80 3.2.1 PMBL-PBA-PMBL linear triblock copolymers......................................................... 81 3.2.2 PBA-PMBL multi-arm block copolymers.................................................................. 88 3.2.3 PBA-PMMA multi-arm block copolymers ................................................................ 95 3.3 SILOXANE-BASED LINEAR COPOLYMERS: GRADIENT OR BLOCK? ............................... 102 3.3.1 Fluorosiloxane-based Copolymers ......................................................................... 102 3.3.2 Vinylsiloxane-based Copolymers............................................................................ 112 4 CONCLUSION .................................................................................................................. 122 BIBLIOGRAPHY....................................................................................................................... 126 LIST OF FIGURES.................................................................................................................... 134 LIST OF TABLES...................................................................................................................... 140 7 Overview The Introduction and Motivation section discusses briefly the development of the study of copolymers
Load more

Recommended publications
  • Synthesis and Self-Assembly of Gradient Copolymers
    Master of Chemical Engineering Thesis Synthesis and Self-Assembly of Gradient Copolymers Kevin Wylie 260358983 Department of Chemical Engineering McGill University Montréal, Québec, Canada A Thesis submitted to McGill University in partial fulfillment of the requirements of the degree of Master of Engineering March 2016 © Kevin Wylie 2016 ABSTRACT Controlled free radical polymerization allows for the fine control of many key properties of polymers such as the molecular weight, dispersity and composition. Consequently, this permits the attainment of interesting microstructures such as block or tapered/gradient copolymers. In particular, nitroxide-mediated polymerization (NMP) was applied and used for the polymerization of methyl methacrylate (MMA) and styrene (St) block and tapered gradient polymers. With the defined composition and molecular weight, such copolymers are able to self-assemble into sub-50 nm domains. In this thesis, gradient copolymers synthesized in semi- batch mode were produced with varying composition and gradient profiles by alternating the rate of St addition and the length of the reaction. Their self-assembly performance was assessed relative to block copolymers with identical molecular properties and found to have similar feature sizes. However, with increasing gradient length, the self-assembly is negatively affected, producing films with very little order and much higher defect densities than block copolymers or polymers with short gradient lengths. i RÉSUMÉ La polymérisation radicale contrôlée permet le contrôle précis de plusieurs propriétés clés des polymères, tels que la masse moléculaire, dispersité et composition. Par conséquent, ce qui permet la réalisation de microstructures intéressants tels que copolymères bloque ou gradient. En particulier, on a appliqué la polymérisation nitroxide-médié (NMP) pour polymériser le méthacrylate de méthyl (MMA) et le styrène (St) en copolymères bloque et gradient.
    [Show full text]
  • Stereoselective Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides
    ARTICLE DOI: 10.1038/s41467-018-03879-5 OPEN Stereoselective photoredox ring-opening polymerization of O-carboxyanhydrides Quanyou Feng 1,2, Lei Yang1, Yongliang Zhong2, Dong Guo3, Guoliang Liu2,3, Linghai Xie 1, Wei Huang1 & Rong Tong 2 Biodegradable polyesters with various tacticities have been synthesized by means of stereoselective ring-opening polymerization of racemic lactide and β-lactones but with 1234567890():,; limited side-chain groups. However, stereoselective synthesis of functional polyesters remains challenging from O-carboxyanhydrides that have abundant pendant side-chain functional groups. Herein we report a powerful strategy to synthesize stereoblock polyesters by stereoselective ring-opening polymerization of racemic O-carboxyanhydrides with the use of photoredox Ni/Ir catalysts and a selected Zn complex with an achiral ligand. The obtained stereoblock copolymers are highly isotactic with high molecular weights ( > 70 kDa) and narrow molecular weight distributions (Mw/Mn < 1.1), and they display distinct melting temperatures that are similar to their stereocomplex counterparts. Furthermore, in one-pot photoredox copolymerization of two different O-carboxyanhydrides, the use of such Zn complex mediates kinetic resolution of the comonomers during enchainment and shows a chirality preference that allows for the synthesis of gradient copolymers. 1 Institute of Optoelectronic Materials, Key Laboratory for Organic Electronics and Information Displays, Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing University of Posts and Telecommunications, 9 Wenyuan Road, Nanjing 210023, China. 2 Department of Chemical Engineering, Virginia Polytechnic Institute and State University, 635 Prices Fork Road, Blacksburg, Virginia 24061, United States. 3 Department of Chemistry, Virginia Polytechnic Institute and State University, 800 West Campus Drive, Blacksburg, Virginia 24061, United States.
    [Show full text]
  • Macromolecular Engineering by Applying Concurrent Reactions with ATRP
    polymers Perspective Macromolecular Engineering by Applying Concurrent Reactions with ATRP Yu Wang 1,2,* , Mary Nguyen 3 and Amanda J. Gildersleeve 1 1 Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA 70504, USA; [email protected] 2 Institute for Materials Research and Innovation, University of Louisiana at Lafayette, Lafayette, LA 70504, USA 3 Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504, USA; [email protected] * Correspondence: [email protected] Received: 5 July 2020; Accepted: 24 July 2020; Published: 29 July 2020 Abstract: Modern polymeric material design often involves precise tailoring of molecular/supramolecular structures which is also called macromolecular engineering. The available tools for molecular structure tailoring are controlled/living polymerization methods, click chemistry, supramolecular polymerization, self-assembly, among others. When polymeric materials with complex molecular architectures are targeted, it usually takes several steps of reactions to obtain the aimed product. Concurrent polymerization methods, i.e., two or more reaction mechanisms, steps, or procedures take place simultaneously instead of sequentially, can significantly reduce the complexity of the reaction procedure or provide special molecular architectures that would be otherwise very difficult to synthesize. Atom transfer radical polymerization, ATRP, has been widely applied in concurrent polymerization reactions and resulted in improved efficiency in macromolecular engineering. This perspective summarizes reported studies employing concurrent polymerization methods with ATRP as one of the reaction components and highlights future research directions in this area. Keywords: macromolecular engineering; ATRP; click chemistry; CuAAC; RAFT; ROMP; ROP; concurrent polymerization 1. Introduction Modern polymeric material design often involves precise macromolecular synthesis to achieve targeted macroscopic material properties.
    [Show full text]
  • N-Heterocyclic Carbene Mediated Zwitterionic Polymerization for Cyclic Polymers
    N-HETEROCYCLIC CARBENE MEDIATED ZWITTERIONIC POLYMERIZATION FOR CYCLIC POLYMERS A DISSERTATION SUBMITTED TO THE DEPARTMENT OF CHEMISTRY AND THE COMMITTEE ON GRADUATE STUDIES OF STANFORD UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Eun Ji Shin July 2011 © 2011 by Eun Ji Shin. All Rights Reserved. Re-distributed by Stanford University under license with the author. This work is licensed under a Creative Commons Attribution- Noncommercial 3.0 United States License. http://creativecommons.org/licenses/by-nc/3.0/us/ This dissertation is online at: http://purl.stanford.edu/tj619sw3147 ii I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Robert Waymouth, Primary Adviser I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Wray Huestis I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Barry Trost Approved for the Stanford University Committee on Graduate Studies. Patricia J. Gumport, Vice Provost Graduate Education This signature page was generated electronically upon submission of this dissertation in electronic format. An original signed hard copy of the signature page is on file in University Archives. iii ABSTRACT Zwitterionic polymerization involves a propagating species with both positively and negatively charged groups. Previous investigations on zwitterionic polymerization concern alternating copolymerization of nucleophilic and electrophilic monomers and polymerization of isolated stable zwitterionic monomers.
    [Show full text]
  • Fundamentals of Reversible Addition– Fragmentation Chain Transfer
    Chemistry Teacher International 2021; 3(2): 3–17 Review article Catherine L. Moad and Graeme Moad* Fundamentals of reversible addition– fragmentation chain transfer (RAFT) https://doi.org/10.1515/cti-2020-0026 Received September 15, 2020; accepted December 14, 2020; published online December 30, 2020 Abstract: Radical polymerization is transformed into what is known as reversible addition–fragmentation chain transfer (RAFT) polymerization by the addition of a RAFT agent. RAFT polymerization enables the preparation of polymers with predictable molar mass, narrow chain length distribution, high end-group integrity and provides the ability to construct macromolecules with the intricate architectures and composition demanded by modern applications in medicine, electronics and nanotechnology. This paper provides a background to understanding the mechanism of RAFT polymerization and how this technique has evolved. Keywords: addition–fragmentation; radical polymerization; RAFT; reversible-deactivation. Introduction This paper aims to provide an understanding of the mechanism of reversible addition–fragmentation chain transfer (RAFT) polymerization without going into full detail on the actual chemicals (i.e., monomers, ini- tiators and control agents) used. It is intended for undergraduates who have some understanding of organic or polymer chemistry and already know about reactive intermediates (e.g., carbon-centered radicals, carbanions), reaction types (e.g., addition reaction, fragmentation reaction, substitution reaction) and polymerization. Radical polymerization is a versatile process that sees widespread use in industry for production of many commodity polymers that include poly(methyl methacrylate) (PMMA, Perspex®), polystyrene, low density polyethylene (LDPE), poly(vinyl chloride) (PVC) and many others. It is compatible with a vast range of monomers, it is tolerant of functionality in the monomers and the polymerization medium, and it can be carried out under a wide range of polymerization conditions (Moad & Solomon, 2006c).
    [Show full text]
  • Functional Spaces in Star and Single-Chain Polymers Via Living Radical Polymerization
    Polymer Journal (2014) 46, 664–673 & 2014 The Society of Polymer Science, Japan (SPSJ) All rights reserved 0032-3896/14 www.nature.com/pj FOCUS REVIEW Functional spaces in star and single-chain polymers via living radical polymerization Takaya Terashima This article reviews recent advances in the creation of functional spaces with core-functionalized star polymers and single-chain folding/crosslinked polymers via living radical polymerization. Various core-functionalized star polymers were efficiently prepared with functional linking agents and monomers to perform unique functions. For example, they can serve as nanoreactors for active and robust catalysis in organic reactions and polymerization and as nanocapsules for selective and stimuli-responsive molecular recognition. Single-chain folding polymers were obtained from the self-folding of amphiphilic random copolymers bearing hydrophilic poly(ethylene glycol) chains and hydrophobic alkyl pendants in water, resulting in unimer micelles with dynamic hydrophobic domains. The folded structure could be further fixed via the intramolecular crosslinking of the hydrophobic interior. In addition, cation template-assisted cyclopolymerization and concurrent tandem living radical polymerization with in situ monomer transesterification were also developed for the one-pot synthesis of cyclopolymers with large in-chain cavities and gradient and sequence-controlled copolymers. Polymer Journal (2014) 46, 664–673; doi:10.1038/pj.2014.57; published online 16 July 2014 INTRODUCTION polymerization,29–35 whereas the microgel cores of divinyl Polymers and macromolecules can provide three-dimensional com- compounds have been conventionally used as a connecting point of partments1–10 and place functional groups in a specific position11 to arm polymers. Beyond such classical understanding, we regard the serve as promising scaffolds for unique functional spaces.
    [Show full text]
  • Thermodynamics and Kinetics of Ring - Opening Polymerization Andrzej Duda and Adam Kowalski
    1 1 Thermodynamics and Kinetics of Ring - Opening Polymerization Andrzej Duda and Adam Kowalski 1.1 Introduction Cyclic monomers that have been polymerized via ring - opening encompass a variety of structures, such as alkanes, alkenes, compounds containing heteroatoms in the ring: oxygen [ethers, acetals, esters (lactones, lactides, and carbonates), and anhydrides], sulfur (polysulfur, sulfi des and polysulfi des), nitrogen [amines, amides (lactames), imides, N - carboxyanhydrides and 1,3 - oxaza derivatives], phos- phorus (phosphates, phosphonates, phosphites, phosphines and phosphazenes), or silicon (siloxanes, silaethers, carbosilanes and silanes). For the majority of these monomers, convenient polymerization conditions have been elaborated, that result in the controlled synthesis of the corresponding polymers [1 – 13] . The ability of a cyclic monomer to polymerize according to the ring - opening mechanism is determined by two equally important factors – the conversion of monomer molecules into macromolecules (of linear or more complex topologies) must be allowed both thermodynamically and kinetically. In practical terms this means that: (i) monomer- macromolecule equilibrium must be shifted to the right- hand (macromolecule) side; and (ii) the corresponding polymerization mechanism should exist, that could enable conversion of the monomer molecules into the polymer repeating units, within the operable polymerization time (Equation 1.1 ). The net equation of the polymerization process reads: n M ...-(m)n-... (1.1) where M denotes the monomer molecule, and m is the macromolecule repeating unit derived from the M monomer; whereas an elementary reaction of the mac- romolecular chain growth can be written as: k p ...-(m) m* (1.2) ...-(m)nm* + M n+1 k d Handbook of Ring-Opening Polymerization.
    [Show full text]
  • Living Ring-Opening Polymerization of O-Carboxyanhydrides: the Search for Catalysts
    Living Ring-Opening Polymerization of O-Carboxyanhydrides: the Search for Catalysts Yongliang Zhong, Rong Tong* Department of Chemical Engineering, Virginia Polytechnic Institute and State University, 635 Prices Fork Road, Blacksburg, Virginia, 24061, United States * Email: [email protected] Abstract Biodegradable poly(α-hydroxy acids) can be synthesized by means of ring-opening polymerization (ROP) of O-carboxyanhydrides (OCAs). Numerous catalysts have been developed to control the living polymerization of OCAs. Here we review the rationale for the use of OCA, the desirable features for and important attributes of catalysts for the ROP of OCAs, and specific examples that have been developed. 1. Introduction Polymers, commonly called plastics, can be categorized as degradable and non- degradable. Non-degradable plastics, mostly from petrochemical resources, tend to have difficulty in recycling and ultimately pollute the environment.1-2 Substantial efforts have been devoted to develop degradable polymers.3 Poly(α-hydroxy acids), including polylactide and polyglycolide, and other polyesters are arguably the most successful examples.4-6 However, the mechanical and thermal properties of these materials still need to be improved to match non- degradable polymers.7-8 Besides efforts in processing with additives or developing new processing techniques,9-15 one major focus in polymer chemistry society is to generate new sets of monomers from natural resources to produce the new degradable polymers that potentially replace many commodity polymers in the market. 16-19 Among these new monomers, 1,3-dioxance-2,4-diones, so-called O- carboxyanhydrides (OCAs), have emerged as an alternative class of highly active monomers for the synthesis of poly(α-hydroxy acids).20-22 OCAs can be prepared from α-amino acid or α- hydroxy acids with a rich variety of side-chain functionalities (Fig.
    [Show full text]
  • Solubility Behaviour of Random and Gradient Copolymers of Di
    Soft Matter View Article Online PAPER View Journal | View Issue Solubility behaviour of random and gradient copolymers of di- and oligo(ethylene oxide) Cite this: Soft Matter, 2020, 16,1066 methacrylate in water: effect of various additives† Maryam Bozorg,a Birgit Hankiewicza and Volker Abetz *ab Poly[oligo(ethylene oxide)] based gradient and random copolymers with different compositions are synthesized via Cu-based atom transfer radical polymerization. The solubility behavior of these copolymers in pure water and in the presence of different salts, surfactants and ethanol is investigated. According to dynamic light scattering results, the lower critical solution temperature (LCST) depends on the structure of the copolymer and changes slightly in the presence of additives. Good cosolvents like ethanol can increase the LCST through dissolving the collapsed copolymer chains to some extent. The same effect is observed for surfactants that make the copolymer solution more stable by preventing aggregation. Above a certain concentration of surfactant, depending on the copolymer structure, the solution is Creative Commons Attribution 3.0 Unported Licence. stable at all temperatures (no LCST). The effect of salts on the solubility of the copolymers follows the Hofmeister series and it is related linearly to the salt concentration. Based on their affinity to the copolymer, the salts can increase or decrease the LCST. There is a considerable difference in phase transition changes for gradient or random copolymers after salt addition. While both copolymers show a Received 11th October 2019, two-step phase transition in the presence of different salts, the changes in the hydrodynamic radius and Accepted 1st December 2019 normalized scattering intensity are rather broad for random compared to gradient copolymers.
    [Show full text]
  • A New Solid-State Nmr Method Reveals the Influence of Chain Structure and Thermal History on the Crystal- Amorphous Interface in Polyethylenes
    A NEW SOLID-STATE NMR METHOD REVEALS THE INFLUENCE OF CHAIN STRUCTURE AND THERMAL HISTORY ON THE CRYSTAL- AMORPHOUS INTERFACE IN POLYETHYLENES By ARIFUZZAMAN TAPASH Bachelor of Science in Applied Chemistry & Chem. Tech. University of Dhaka Dhaka 2005 Masters of Science in Applied Chemistry & Chem. Eng. University of Dhaka Dhaka 2006 Submitted to the Faculty of the Graduate College of the Oklahoma State University in partial fulfillment of the requirements for the Degree of DOCTOR OF PHILOSOPHY May, 2016 A NEW SOLID-STATE NMR METHOD REVEALS THE INFLUENCE OF CHAIN STRUCTURE AND THERMAL HISTORY ON THE CRYSTAL-AMORPHOUS INTERFACE IN POLYETHYLENES Dissertation Approved: Dr. Jeffery L. White Dissertation Adviser Dr. Frank D. Blum Dr. Toby Nelson Dr. Jimmie Weaver Dr. Rob Whiteley ii Name: ARIFUZZAMAN TAPASH Date of Degree: MAY, 2016 Title of Study: A NEW SOLID-STATE NMR METHOD REVEALS THE INFLUENCE OF CHAIN STRUCTURE AND THERMAL HISTORY ON THE CRYSTAL-AMORPHOUS INTERFACE IN POLYETHYLENES. Major Field: CHEMISTRY Abstract: Clear understanding of polymer morphology is important as it is directly related to the final properties. A simple solid-state NMR method is presented in this contribution to quantitatively determine the distribution of solid polyethylene chain segments in different morphological regions. The rigid chain in the crystalline phase with all-trans chain conformations, the non-crystalline (amorphous) mixed trans-gauche chains undergoing essentially isotropic reorientation, all-trans chains with higher mobility (mobile all-trans), and non-crystalline chains with limited mobility (constrained amorphous) fractions were reliably quantified using a new double-acquisition solid-state 13C NMR experiment. A wide range of well-characterized PE samples was studied, which reveals that the amount of interface region increases with the chain length of linear metallocene-PE.
    [Show full text]
  • 1 Gradient Copolymers
    Gradient Copolymers – Preparation, Properties and Practice Md. Mahbub Alam, a Kevin S. Jack, b David J.T. Hill,a,c Andrew K. Whittaker a,d and Hui Peng a,d * a Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Australia; b Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, Australia; c School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia; d ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Brisbane, Australia. Corresponding author: Hui Peng; Email: [email protected] Abstract: Gradient copolymers are members of a unique class of copolymer in which the monomer composition changes gradually from one end of the polymer chain to the other. In general, the properties of copolymers are strongly dependent on composition and sequence distribution, and hence gradient copolymers can exhibit unique properties compared to those of block and statistical copolymers. This review presents an overview of the methods of synthesis of gradient copolymers using the range of available polymerization techniques, and compares and contrasts the properties of gradient copolymers with properties of the analogous block and statistical copolymers. Keywords: Gradient copolymers, controlled radical polymerization, interfacial behaviour, critical micelle concentration, glass transition temperature. 1. Introduction to Gradient Copolymers Polymer chain microstructure plays an important role in determining the properties of polymeric materials [1]. Extensive theoretical and experimental investigations have suggested that beside the overall copolymer composition, the distribution of monomer units along the polymer chains can be an important microstructural parameter to control the physical and functional properties of polymeric materials by fine-tuning the nanomorphologies of the polymer chains [2-7].
    [Show full text]